It is generally not practical in a communications system to generate and work with frequencies that are the same as the transmit frequency. Depending on the type of system, the transmit frequencies may be greater than 100 MHz.
The generated signals, therefore, are mixed from an intermediate frequency to a higher, transmit frequency by an upconverter circuit. The upconverter may introduce noise and frequency response distortion to the signal prior to transmission.
Distortion may also be added to a signal prior to transmission by any analog component that processes the signal. For example, a digital to analog converter can introduce errors and distortion.
A modulation error ratio (MER) is one metric used in the art to indicate a signal's fidelity. The frequency response distortions degrade the MER of the transmitted signal causing the receiver to receive a signal that may be difficult to interpret or demodulate properly.
The MER may be increased by manually adjusting components in the analog circuitry or by using more accurate analog components. Both approaches result in an increase in the expense of manufacturing the electronic device. There is a resulting need in the art to economically reduce frequency response distortions, thereby increasing MER, prior to transmission of a signal.